Fructose-1, 6 Diphosphate is anaerobically metabolized to yield 4 mol of ATP. The vaso-occlusive crises of sickle cell disease are characterized by tissue ischemia due to hypoxemia. Hypoxemia promotes the change from flexible erythro-cytes to rigid sickle cells and aggravates tissue ischemia. Providing energy by increasing intracellular ATP may prevent sickling and shorten crises. A dose escalation study will be performed in three stages. This pilot study should establish the tolerability of FDP and the efficacy and safety of this agent.